Spray nozzle type devices customarily consist of a nozzle body extending from a fluid inlet end to a fluid outlet end the interior of which body defines a central bore housing, among other possible components, a swirl device and an orifice disc.
It is well known for an outlet face of the orifice disc to abut a landing defined by an inner periphery of the nozzle cap about a central bore and to be provided with a seal between the disc and cap.
In the prior art it has been known to provide a compressive seal at the front of the nozzle, between the inner housing and the orifice disc, using a fiat washer seal.
Such a washer seal does not provide for particularly reliable sealing at elevated pressure and temperature, with the flat seal likely to be squeezed out of the mating surfaces under some conditions.
Other types of sealing means are used in spray nozzle assemblies for example a new system has been developed which uses two independent O ring seals in compression (as opposed to a common axial body seal coupled with a front compressive seal) to form the pressure containing function for the entire nozzle assembly, whereby one O ring resides at the front of the assembly within the nozzle cap, and provides a seal between the orifice disc and the inner nozzle cap housing, and the other seal exists at the rear sealing face of the nozzle cap housing where it engages the face of the housing body via a screwed mechanism, forming the final seal.
This new sealing method allows for much higher pressure ratings than were possible with the prior art.
A further improved sealing method used in the prior art is an O ring seal groove situated inside the inner cap housing within the lower periphery of the nozzle cap, designed to conform to known sealing gland dimension standards, and allowing for correct sealing between the orifice disc and the inner cap housing. This arrangement however reduces the pressure retaining wall thickness between the inner depth of the o-ring groove and the outer surface of the housing, whose outer profile form is restricted by the need to prevent impeding the emitted spray from the orifice disc, thus compromising the mechanical strength of the housing itself.
In this prior art, the nozzle disc typically abuts a single radial mating surface inboard of the O-ring groove in the nozzle cap, with the outer diameter of the orifice disc being free and unsupported at the outer O-ring groove, which is flush with the accommodating diameter of the disc housing bore and larger In diameter than the orifice disc due to normal clearance requirements.
This typical arrangement provides little mechanical support for the compressive forces required to create an adequate face to face seal without gaps. Also, when such required compressive forces are applied, a bending moment is applied to this radial mating surface inboard of the O-ring groove, placing a bending stress upon the thinner area between the outer face of the component housing the seal groove, and the innermost O-ring groove depth, which can result in failure of this innermost radial mating surface, and in worst case scenarios, cause this entire middle section to push outward and fracture away. Thus this arrangement is not conducive to high pressure operation.
A method used to reduce the need for an O-ring groove in the inner cap, was to simply use an O-ring in compression, much like the flat washer, and not provide any sealing grooves for the proper sealing of the parts. In this case a cavity is provided between the disc and the housing cap. This variation has distinct pressure limitations where the sealing cavity formed conforms to no known sealing conventions.